The present invention relates to automatic injectors for delivering medicament to an injection site. In particular, the present invention is directed to an automatic injector assembly for quickly combining a liquid material with a dry material to form a liquid medicament for delivering the medicament to an injection site. In accordance with the present invention, the automatic injector assembly includes a pair of movable plunger assemblies within the injector assembly for pressurizing the liquid injection solution and compressing the dry medicament.
An automatic injector is a device for enabling an individual to self-administer a dosage of medicament into his or her flesh. The medicament is usually stored in liquid form. The advantage of automatic injectors is that they contain a measured dosage of a liquid medicament in a sealed sterile cartridge and can be utilized for delivering the medicament into the flesh during emergency situations. Another advantage of automatic injectors is that the self-administration of the medicament is accomplished without the user initially seeing the hypodermic needle through which the medicament is delivered and without having the user to manually force the needle into his or her own flesh.
There are drawbacks associated with the storage of medicament in liquid form. Some medicaments are not stable in liquid form. Furthermore, some liquid medicaments typically have a shorter shelf life than their solid counterparts. Others have developed automatic injectors that store the medicament in solid form and a liquid injection solution. These injectors, disclosed for example in U.S. Reissue Pat. No. 35,986, entitled xe2x80x9cMultiple Chamber Automatic Injector,xe2x80x9d (the disclosure of which is incorporated herein specifically by reference), however, require the user of the injector to expedite dissolution of the solid component by manually shaking the liquid component and the solid component immediately prior to injection. This increases the time needed to administer a dose of medicament. Furthermore, the improper mixing of the medicament with the liquid injection solution may release an insufficient dose of medicament. There is a need for an automatic injector that stores medicament in solid form that does not require manual premixing by the user. Furthermore, rapid delivery of the medicament is needed for emergency medical situations (e.g. nerve gas and chemical agent poisoning).
It is therefore an object of the present invention to provide an automatic injector device that stores medicament in a solid form for increased shelf life.
It is another object of the present invention to provide an automatic injector device that automatically mixes a solid medicament with a liquid injection solution upon activation.
It is another object of the present invention to provide an automatic injector device that pressurizes a stored liquid injection solution upon activation of the automatic injector device.
It is another object of the present invention to provide an automatic injector device that compresses the dry medicament upon pressurization of the stored liquid injection solution.
It is another object of the present invention to provide an automatic injector device that minimizes residual space within the injector device to limit the trapping of dry medicament.
It is another object of the present invention to provide an automatic injector device that permits the injection of a medicament without the need for shaking the automatic injector device.
Additional objects and advantages of the invention are set forth, in part, in the description which follows, and, in part, will be apparent to one of ordinary skill in the art from the description and/or practice of the invention.
In response to the foregoing challenges, applicants have developed an innovative automatic injection device having both wet and dry storage compartments. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The present invention is directed to an automatic injection device containing a pre-loaded charge of medicament for automatically self-administering the medicament upon actuation thereof. The injection device includes a housing assembly, a dry compartment located within the housing for storing a predetermined dry charge of dry medicament therein, and a wet compartment located within the housing for storing a predetermined amount of liquid injection solution therein. The injection device further includes an activation assembly that enables the pressurization of the liquid injection solution in the wet compartment. The activation assembly also enables the compression of the dry medicament within the dry compartment upon activation of the automatic injection device. The compression of the medicament occurs independently of the application of pressure on the liquid injection solution. The activation assembly further facilitates passage of the liquid injection solution from the wet compartment to the dry compartment upon activation of the automatic injection device. The injection device also includes a needle assembly for dispensing the liquid injection solution containing the medicament dissolved therein.
In accordance with present invention, it is contemplated that the activation assembly may include a first pressure element that applies pressure to the liquid injection solution within the wet compartment upon activation of the automatic injection device. The activation assembly may further include a second pressure element that compresses the dry medicament within the dry compartment upon activation of the automatic injection device. The second pressure element provides a barrier between the wet compartment and the dry compartment to prevent the transfer of the liquid injection solution from the wet compartment to the dry compartment prior to activation of the automatic injection device.
The activation assembly may further include a linking member for transmitting a force from the first pressure element and the collet to the second pressure element to facilitate compression of the dry medicament. It is contemplated that the first pressure element frictionally engages the linking element to apply a force from the first pressure element to the linking element. The application of pressure on the second pressure element through the linking element occurs such that the dry medicament may be compressed prior to the pressurization of the liquid injection solution. The linking element is slidably received within an aperture within the first pressure element. The linking member is adapted to come in or be in contact with the second pressure element. The linking element may include a stepped surface or have a slight change in diameter on the shaft of the linking member such that the first pressure element contacts the stepped surface/change in diameter to initially drive the second pressure element, which ensures pressure on the dry medicament. The force of the spring assembly may be sufficient to overcome the forces associated with the diameter change of the linking element, whereby the first pressure element slides along the linking element to pressurize the liquid injection solution and force the solution into the dry compartment.
The present invention is also directed to a method of mixing a dry medicament with a liquid injection solution in an automatic injection device for administering a dosage of medicament to a user. The automatic injection device includes a dry compartment for storing the dry medicament prior to mixing, a wet compartment for storing a supply of liquid injection solution prior to mixing, and a needle assembly for transferring a mixture of dissolved dry medicament and the liquid injection solution to a user. The method includes activating the automatic injection device, pressurizing the liquid injection solution in the wet compartment and simultaneously compressing the dry medicament in the dry compartment. The method further includes opening a fluid path between the wet compartment and the dry compartment to permit the passage of the liquid injection solution from the wet compartment to the dry compartment, dissolving the dry medicament in the liquid injection solution within the dry compartment, and transferring the mixture of the dissolved dry medicament and the liquid injection solution through the needle assembly to the user.
In accordance with the present invention, the pressurization of the liquid injection solution in the wet compartment may include applying a force on a first pressure element within the wet compartment. The compression of the dry medicament in the dry compartment may include transferring a force from the first pressure element to a second pressure element, and compressing the dry medicament with the second pressure element. The opening of the fluid path between the wet compartment and the dry compartment may include moving the second pressure element from a first position to permit the passage of the liquid injection solution from the wet compartment to the dry compartment around the second pressure element.